The present invention relates to a display device for a push button assembly in which a window is disposed at the push button and a display surface is disposed oppositely to and inside with respect to this window, whereby the operating state of the push button is displayed on the window by opening or closing shutters disposed between the display surface and the window.
There has conventionally been known a display device of this kind, for example, as disclosed in the U.S. Pat. No. 3,715,548 where the display member is disposed in the push button having a window such that the display surface of the display member is faced to the window, and the covering shutters are disposed between the window and the display surface, said covering shutters adapted to swing, responsively to the axial relative movement of the push button with the display member, between two positions, i.e., a first position where the display surface is screened from the window and a second position where the display surface is exposed to the window.
In such a conventional one, however, the covering shutters are rotatably pivoted in the push button and are adapted to open and close by means of the display member which is adapted to move forward and rearward with respect to the push button. It has therefore been necessary to assemble the shutters in the narrow and small push button housing in a skilful manner such that the shutters be smoothly rotated therein. This presents a problem of being cumbersome in assembly and time-consuming.
Since, in a display device of this kind, the shutters are opened and closed between the window of the push button and the display surface, it may be proposed that, for example, a photo-electric converting element connected to the automatic brightness control circuit of a television set is disposed at the display surface and the automatic brightness control circuit is arranged so as to operate only when the photo-electric converting element is exposed to the window by opening the shutters.
In a conventional display device, however, a pair of shutters are merely disposed in the double-leafed hinged manner and a clearance may therefore be produced easily between the abutted ends of the shutters, thus provoking a possibility of light penetrating the inside of the push button even if the shutters are closed. This therefore presents a problem that it is difficult to permit the automatic brightness control circuit to be operable by applying light onto the photo-electric converting element only when the shutters are opened with the push button depressed.